Manufacturing method for polarizing conversion elements

ABSTRACT

A number of k sets of light transmissive members are prepared, k being an integer of 2 or greater, where each set thereof may consist of a plurality of first light transmissive plates and a plurality of second light transmissive plates, and (K+1) third light transmissive plates having a greater thickness than those of the first and the second light transmissive plate. A composite plate member is produced by alternately arranging and bonding one set of the plurality of first light transmissive plates and the plurality of second light transmissive plates to each of the spaces between the (K+1) third light transmissive plates, and alternately arranging a plurality of polarization separating films and a plurality of reflecting films on each interface in the composite plate member. A block substrate having a light receiving surface and a light emitting surface is produced by cutting the composite plate member along a first section parallel to a surface inclining at a predetermined angle with the surface of the composite plate member, the light receiving and light emitting surfaces being parallel to the first section. The light receiving surface and the light emitting surface of the block substrate are polished, and k light transmissive blocks are produced from one block substrate by dividing the block substrate at the positions of the third light transmissive plates disposed inside the block substrate.

This is a Continuation of Application Ser. No 09/609,069 filed Jun. 30,2000, now U.S. Pat. No. 6,436,214. The entire disclosure of the priorapplication(s) is hereby incorporated by reference herein in itsentirety.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a manufacturing method for a polarizingconversion element for converting incident non-polarized light intospecified polarized light.

2. Description of Related Art

In a projector, a light-modulating device for modulating lightcorresponding to image signals is used. As the light-modulating device,the type of using only one type of linear polarized light, such as atransmissive liquid crystal panel and a reflective liquid crystal panel,is usually used. In the projector which only uses such one type oflinear polarized light, a polarizing conversion element for convertingemitted non-polarized light from a light source into one type of alinear polarized light component (S-polarized light component orP-polarized light component, for example) is provided.

FIGS. 8(A)-(B) are schematic representations showing a polarizingconversion element 320. FIG. 8(A) shows the polarizing conversionelement 320 in the x-z plane, while FIG. 8(A) shows the polarizingconversion element 320 in the x-y plane.

The polarizing conversion element 320 may consist of a polarizing beamsplitter array (polarized light separating element) 340 and a pluralityof λ/2 phase films 381 selectively arranged on portions of emittingsurface of the polarizing beam splitter array 340. The polarizing beamsplitter array 340 has a height of h and a shape in which a plurality ofcolumn-shaped light transmissive members 324, each having aparallelogram cross-section, are sequentially bonded to each other, andcolumn-shaped light transmissive members 325 and 326, each having atrapezoidal cross-section, are respectively bonded to the two ends ofthe bonded members 324. Polarization separating films 331 and reflectingfilms 332 are alternately formed on each of boundary surfaces betweenlight transmissive members 324, 325, and 326. The λ/2 phase films 381are selectively arranged at mapping portions in the x-direction ofemitting light from the polarization separating film 331 or thereflecting film 332. In this example, the λ/2 phase films 381 areselectively arranged at mapping portions in the x-direction of emittinglight from the polarization separating film 331.

The polarizing conversion element 320 separates incident light on thepolarization separating film 331 into an S-polarized light component anda P-polarized light component. The S-polarized light is reflected by thepolarization separating film 331 and is further reflected by thereflecting film 332 to be emitted therefrom. On the other hand, theP-polarized light component is allowed to pass through the polarizationseparating film 331 just as it is. On the emitting surface of thetransmitted light from the polarization separating film 331, the λ/2phase film 381 is arranged, whereby the P-polarized light component istransformed to the S-polarized light component to be emitted therefrom.Therefore, a set of the polarization separating film 331, the reflectingfilm 332, and the λ/2 phase film 381, which adjoin each other,corresponds to one polarizing conversion unit. In addition, thepolarizing conversion element 320 in this example has three lines ofpolarizing conversion unit 350 and one line of dummy unit 350 d. In sucha manner, the polarizing conversion element 320 is an optical elementfor converting incident light on the polarization separating film 331into substantially one kind of a linearly polarized light component.

SUMMARY OF THE INVENTION

FIG. 9 is a schematic representation showing a manufacturing example forthe polarizing beam splitter array 340. In the polarizing beam splitterarray 340, for example, a first glass plate 321 having the polarizationseparating film 331 and the reflecting film 332 formed thereon and asecond glass plate 322 having no film formed thereon are alternatelybonded to each other by an optical adhesive 327, so that thepolarization separating film 331 and the reflecting film 332 arealternately arranged. Then, an ultra violet ray (UV ray) is irradiatedthereon to cure the optical adhesive 327. At this time, third glassplates 323 having a different thickness from that of the first and thesecond glass plates 321 and 322 are used as first and the last plates ofthe bonded plates, to form a composite plate member 400. Lighttransmissive blocks are cut substantially in parallel with each otheroff the composite plate member 400 formed as above along sections (shownby broken lines in the drawing) inclining at the predetermined angle “θ”with the surface of the composite plate member 400, using a multi-wiresaw or a multi-blade saw. The value “θ” is preferably about 45°. Here,“the surface of the composite plate member 400” indicates the surface ofthe third plates 323 bonded at the both ends. Protruding portions ofboth ends of the block are cut off by a dicing saw or a laser cuttingapparatus so that the block has a substantially rectangular shape.Surfaces (cutting sections) of the light transmissive block cut in sucha manner are polished to obtain the polarizing beam splitter array 340(FIGS. 8(A)-(B)). In addition, portions formed by the first and thesecond glass plates 321 and 322 correspond to the light transmissivemembers 324, while one of the portions formed by the third glass plates323 at one of the two ends corresponds to the light transmissive member325, and the other thereof at the other end corresponds to the lighttransmissive member 326. The thickness of the third glass plate 323corresponding to the light transmissive members 325 may be differentfrom that of the third glass plate 323 corresponding to the lighttransmissive members 326.

In addition, the polarizing beam splitter array may be referred to as “alight transmissive block” below.

Conventionally, the polarizing conversion element has been manufacturedin the manner described above to improve efficiency. However, a furtherimprovement in manufacturing efficiency is desirable.

The present invention is made to at least solve the above-mentionedproblems, and it is an object of the present invention to at leastprovide a technology to manufacture a polarizing conversion element moreefficiently.

Accordingly, a first method for manufacturing a polarizing conversionelement according to the present invention may consist of the steps of:

preparing k sets of light transmissive members, k being an integer of 2or greater, where each of the sets may consist of a plurality of firstlight transmissive plates and a plurality of second light transmissiveplates having substantially a same thickness as that of the first lighttransmissive plates;

preparing (K+1) third light transmissive plates having a greaterthickness than those of the first light transmissive plates and thesecond light transmissive plates;

producing a composite plate member by alternately arranging and bondingone set of the plurality of first light transmissive plates and theplurality of second light transmissive plates to each of spaces betweenthe (K+1) third light transmissive plates, and alternately arranging aplurality of polarization separating films and a plurality of reflectingfilms on each interface between the first light transmissive plates, thesecond light transmissive plates and third light transmissive plates inthe composite plate member;

producing a block substrate having a light receiving surface and a lightemitting surface by cutting the composite plate member along a firstsection parallel to a surface inclining at a predetermined angle with asurface of the composite plate member, the light receiving surface andthe light emitting surface being in parallel to the first section;

polishing the light receiving surface and the light emitting surface ofthe block substrate; and

producing k light transmissive blocks from the one block substrate bydividing the block substrate at positions of the third lighttransmissive plates disposed inside the block substrate.

A second method for manufacturing a polarizing conversion elementaccording to the present invention may consist of the steps of:

preparing k sets of light transmissive members, k being an integer of 2or greater, each of the sets comprising a plurality of first lighttransmissive plates and a plurality of second light transmissive plates;

preparing (K+1) third light transmissive plates having a greaterthickness than those of the first light transmissive plates and thesecond light transmissive plates;

producing a composite plate member by alternately arranging and bondingone set of the plurality of first light transmissive plates and theplurality of second light transmissive plates to each of spaces betweenthe (K+1) third light transmissive plates, and alternately arranging aplurality of polarization separating films and a plurality of reflectingfilms in each interface between the first light transmissive plates, thesecond light transmissive plates and the third light transmissive platesin the composite plate member;

producing a block substrate having a light receiving surface and a lightemitting surface by cutting the composite plate member along a firstsection parallel to a surface inclining at a predetermined angle with asurface of the composite plate member, the light receiving surface andthe light emitting surface being in parallel to the first section; and

producing k light transmissive blocks from one of the block substratesby dividing the block substrate at positions of the third lighttransmissive plates that are disposed inside the block substrate.

In the conventional manufacturing method, 2·k third light transmissiveplates have to be prepared in order to produce k light transmissiveblocks. However, in the manufacturing methods according to the presentinvention, (K+1) third light transmissive plates are enough to beprepared, whereby the number of parts for producing the polarizingconversion element can be reduced, resulting in reduction in themanufacturing cost.

In particular, according to the first manufacturing method of thepresent invention, a block substrate including k light transmissiveblocks per one substrate is produced from a composite plate member;after the produced block substrate is polished, k light transmissiveblocks per one substrate can be produced. Thereby, the number of stepsfor cutting the composite plate member and polishing the light receivingand light emitting surfaces can be reduced to be 1/k compared with thatin producing k light transmissive blocks by a conventional manufacturingmethod, so that the polarizing conversion element can be moreefficiently manufactured than ever.

In addition, preparing the k sets of light transmissive members maypreferably consist of forming the polarization separating film on afirst surface of the first light transmissive plate, and forming areflecting film on a second surface of the first light transmissiveplate. Also, preferably, preparing the k sets of light transmissivemembers may consist of forming a polarization separating film on onesurface of the first light transmissive plate, and forming a reflectingfilm on one surface of the second light transmissive plate.

In either way, a plurality of polarization separating films and aplurality of reflecting films can be alternately arranged on eachinterface between light transmissive plates.

The above-mentioned manufacturing methods may further consist ofdividing a light transmissive block of the light transmissive blocksproduced from the one of the block substrates into a plurality of lighttransmissive blocks by cutting the light transmissive block along asecond section in parallel with a surface substantially perpendicular toa longitudinal direction of the plurality of polarization separatingfilms and the plurality of reflecting films arranged inside the lighttransmissive block.

In this manner, a plurality of light transmissive blocks can be producedfrom one light transmissive block produced, thereby enabling thepolarizing conversion element to be manufactured more efficiently.

Further, the polarizing conversion element manufactured by above methodsmay be employed by a projector. In this manner, resulting in reductionin the manufacturing cost for manufacturing the projector and enablingthe projector to be manufactured more efficiently.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(A)-(C) include schematic representations showing first to thirdglass plates 321, 322, and 323 used for manufacturing a polarizingconversion element 320;

FIGS. 2(A)-(B) include schematic representations showing a process ofproducing a first glass plate 321 a on which a polarization separatingfilm 331 and a reflecting film 332 are formed;

FIGS. 3(A)-(B) include schematic representations showing a process ofproducing a composite plate member 500 so as to produce a blocksubstrate 520;

FIGS. 4(A)-(C) include schematic representations showing a process ofproducing light transmissive blocks 340 from the block substrate 520;

FIG. 5 is a schematic representation showing another method formanufacturing the composite plate member 500 shown in FIGS. 3(A)-(B).;

FIG. 6 is a front view of the light transmissive block 340;

FIG. 7 is a block diagram showing a principal part of a projector whichmay consist of a polarizing conversion element produced by themanufacturing method according to the present invention;

FIGS. 8(A)-(B) include schematic representations for showing a structureof the polarizing conversion element 320; and

FIG. 9 is a schematic representation for showing a manufacturing methodexample of a polarizing beam splitter array 340.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A. A Method for Manufacturing Polarizing Conversion Elements:

A method according to the present invention will be described below byway of an example of manufacturing of the polarizing conversion element320, shown in FIGS. 8(A)-(B), which may consist of three lines ofpolarizing light conversion units 350 and one line of a dummy unit 350d. FIGS. 1(A) to 4(C) are schematic representations showingmanufacturing processes of the polarizing conversion element 320.

First, k sets of three first glass plates and two second glass plates,and the (k+1) third glass plates 323 are prepared (where “k” is aninteger of 2 or greater). The following example will be described ask=2, that is, three third glass plates 323 are prepared.

As shown in FIGS. 1(A) to (C), the first glass plate 321, the secondglass plate 322, and the third glass plate 323 are rectangular-shapedglass plates having the longitudinal length “m” and the transverselength “1”. The thickness “d2” of the second glass plate 322 issubstantially the same as that “d1” of the first glass plate 321. Thethickness “d3” of the third glass plate 323 is larger than that “d1” ofthe first glass plate 321. The meaning of “substantially the same”indicates that differences in the length are not more than severalpercent. In addition, the thickness “d1” of the first glass plate 321and that “d2” of the second glass plate 322 are determined byconsidering the thickness of the optical adhesive 327 so thatpolarization separating films 331 and reflecting films 332 are arrangedat equal intervals when the first glass plate 321 and the second glassplate 322 are alternately bonded to each other, as will be describedlater.

In addition, the first to third glass plates 321, 322, and 323 areequivalent to the first to third light transmissive plates according tothe present invention.

Next, as shown in FIG. 2(A), on one surface of the first glass plate321, the polarization separating film 331 is formed, while, as shown inFIG. 2(B), on the opposite surface thereof, the reflecting film 332 isformed to form a first glass plate 321 a having the polarizationseparating film 331 and the reflecting film 332 formed thereon.

The polarization separating film 331 may be formed by depositing adielectric multi-layer film, and the reflecting film 332 may be formedby depositing a dielectric multi-layer film which may be the same as ordifferent from the dielectric multi-layer film for the polarizationseparating film 331. In addition, the reflecting film 332 may also beformed by an evaporating process of a metallic reflecting film such asaluminum.

Then, as shown in FIG. 3(A), in each of spaces between three third glassplates 323, three first glass plates 321 a and two second glass plates322 are alternately arranged so as to be bonded together by the opticaladhesive 327 so that the polarization separating films 331 and thereflecting films 332 are alternately arranged on each of interfacesbetween glass plates 321, 322, and 323 to form a composite plate member500. The optical adhesive 327 is cured by irradiation of an ultra violetray.

By cutting the composite plate member 500 thus produced along firstsections c1 (shown by broken lines in the drawing) inclining at apredetermined angle “θ” with the surface of the composite plate member500 substantially parallel with each other by using a multi-wire saw ora multi-blade saw, for example, a block substrate 520 shown in FIG. 3(B)is cut. Here “the surface of the composite plate member” indicates thesurface of the third plates 323 bonded at the both ends. The value “θ”is preferably about 45°, In addition, surfaces parallel with the firstsections of the block substrate 520 cut in such a manner are equivalentto a light receiving surface 522 and a light emitting surface 524.

Then as shown in FIG. 4(A), protruding portions (portions of equivalentsto the third glass plates 323) on both ends of the block substrate 520are cut off by a dicing saw or a laser cutting apparatus so that theblock substrate 520 has a substantially rectangular shape, to form asubstantially rectangular block substrate 520 a as shown in FIG. 4(B).After grinding and polishing surfaces of the block substrate 520 a, theblock substrate 520 a is divided at the positions within the portionformed by the third glass plate 323 disposed inside the block substrate520 a by a dicing saw or a laser cutting apparatus to thereby producetwo light transmissive blocks 340 (polarizing beam splitter arrays) fromthe one block substrate 520 a, as shown in FIG. 4(C). At this time,although the effectiveness of the economizing steps will be reduced, thesurface grinding and polishing may be performed after the division ofthe substantially rectangular block substrate 520 a shown in FIG. 4(B).

On the light emitting surface of the light transmissive block 340(polarizing beam splitter array) formed as above, the λ/2 phase films381 are selectively bonded thereon, as shown in FIG. 8(A), therebyenabling the polarizing conversion element 320 to be formed.

In the above-mentioned manufacturing method, the block substrate 520 aincluding two light transmissive blocks 340 is produced from thecomposite plate member 500. After grinding and polishing the producedblock substrate 520 a, two light transmissive blocks 340 from one blocksubstrate 520 a can be produced. Therefore, one step of cutting thecomposite plate member 500 and one step of grinding and polishing thelight receiving surface 522 and the light emitting surface 524 of theblock substrate 520 a can be eliminated in comparison with the steps formanufacturing two light transmissive blocks 340 by the conventionalmanufacturing method (FIG. 9). Accordingly, the light transmissiveblocks 340 can be more efficiently manufactured than previouslypossible. Also, in order to produce the two light transmissive blocks340 by the conventional manufacturing method, four of the third glassplates 323 (FIG. 9) have to be prepared. However, in the above-mentionedmanufacturing method, the number of the required third glass plates 323can be reduced to be three thereby enabling the number of parts formanufacturing the polarizing conversion element 320 to be reduced,resulting in reduction in the manufacturing cost.

In addition, the manufacturing method has been described in an examplein which two light transmissive blocks 340 are produced from one blocksubstrate 520 a. However, it is not limited thereto. By preparing threesets of three first glass plates 321 and two second glass plates 322,and four third glass plates 323 to produce a composite plate member, ablock substrate including the three light transmissive blocks 340 may beproduced from the produced composite plate member. Also, after grindingand polishing the produced composite plate member, the three lighttransmissive blocks 340 may be produced from one composite plate member.That is, in the above-mentioned manufacturing method, by preparing ksets (herein “k” is referred to an integer of 2 or more) of the threefirst glass plates 321 and the two second glass plates 322, and the(K+1) third glass plates 323 to produce a composite plate member, ablock substrate including the k light transmissive blocks 340 may beproduced from the produced composite plate member. After grinding andpolishing the produced composite plate member, the k light transmissiveblocks 340 may be produced from one composite plate member. In such amanner, the polarizing conversion element 320 can be more efficientlymanufactured than being previously possible. Also, the number of therequired third glass plates 323 can be reduced to be (K+1) from 2kplates in the conventional manufacturing method, thereby enabling thenumber of parts for manufacturing the polarizing conversion element tobe reduced, resulting in reduction in the manufacturing cost.

Also, the method has been described in the context in which k sets ofthe three first glass plates 321 and the two second glass plates 322 areprepared. However, it is not limited thereto. K sets of a plurality offirst glass plates 321 and a plurality of second glass plates 322 may beprepared. Thereby, the polarizing conversion element having multiplelines of polarizing conversion units can be efficiently manufactured.

In addition, the manufacturing method has been described in the contextin which the third glass plates 323 have the same thickness; however, itis not limited thereto. For example, the thickness of the third glassplates 323 disposed at the two ends may be different from that of thethird glass plates 323 disposed inside. Also, plates having a differentthickness may be used depending on which ends they are disposed on. Thatis, a third glass plate 323 having different thicknesses may be useddepending on the position it is placed in.

Further, the manufacturing method has been described in the context inwhich the thickness d1 of the first glass plates 321 and the thicknessd2 of the second glass plates 322 are substantially the same; however,d1 and/or d2 may be the same with regard to the thickness of the opticaladhesive 327. Moreover, the manufacturing method has been described inthe context in which the light transmissive block 340 is produced aftergrinding and polishing the surface of the block substrate 520 a;however, the light transmissive block 340 may be produced withoutgrinding and polishing the surface of the block substrate 520 a. In thelatter case, the surface of the light transmissive block 340 is grindedand polished.

FIG. 5 is a schematic representation showing a different manufacturingmethod for the composite plate member 500 shown in FIG. 3. This is amethod for forming and bonding the reflecting film 332 to the surface ofthe second glass plate 322 and the third glass plate 323 in FIGS.3(A)-(B) that is attached via optical adhesive 327 to the side of thefirst glass plate 321 a where reflecting film 332 is.

By this method, substantially the same composite plate member 500′ asthe composite plate member 500 shown in FIG. 3 can also be manufactured.In addition, the composite plate member 500′ has the same functionsexcept for having the different positional relationship between thereflecting film 332 and the optical adhesive 327.

FIG. 6 is a front view of the light transmissive block 340 manufacturedby the above-mentioned manufacturing method. When the light transmissiveblock 340 manufactured by the manufacturing method is cut, by a dicingsaw or a laser cutting apparatus, parallel to a second sectionsubstantially parallel to the direction in which the polarizationseparating films 331 and the reflecting films 332 are arranged, aplurality of light transmissive blocks 340 can be further manufactured.For example, when the height “h” of the polarizing conversion element320 is ½ of the height “1” of the light transmissive block 340, twolight transmissive blocks can be manufactured by dividing the lighttransmissive block 340 into two.

In this method, as well as the foregoing method, k sets of the threefirst glass plates 321 and the two second glass plates 322 are prepared;however, the method is not limited thereto. K sets of a plurality offirst glass plates 321 and a plurality of second glass plates 322 may beprepared. Thereby, the polarizing conversion element having multiplelines of polarizing conversion units can be efficiently manufactured. Inaddition, in this method, the third glass plates 323 have the samethickness; however, the method is not limited thereto. For example, thethickness of the third glass plates 323 disposed at the two ends may bedifferent from that of the third glass plates 323 disposed inside. Also,plates having different thicknesses may be used depending on which endsthey are disposed on. That is, third glass plates 323 having differentthicknesses may be used depending on the position they are placed in.

Further, in this method, the thickness d1 of the first glass plates 321and the thickness d2 of the second glass plates 322 are substantiallythe same; however, d1 and/or d2 may be the same with regard to thethickness of the optical adhesive 327. Moreover, in this method, thelight transmissive block 340 is produced after grinding and polishingthe surface of the block substrate 520 a; however, the lighttransmissive block 340 may be produced without grinding and polishingthe surface of the block substrate 520 a. In the latter case, thesurface of the light transmissive block 340 is grinded and polished.

B. A Structure of Projector:

FIG. 7 is a block diagram showing a principal part of a projector whichmay consist of a polarizing conversion element produced by themanufacturing method according to the present invention. The projector800 may consist of a polarization-illuminating device 50, dichroicmirrors 801 and 804, a reflecting mirror 802, a light guide 850consisting of relay lenses 806, 808, and 810, and reflecting mirrors 807and 809, three light valves 803, 805, and 811, a cross-dichroic prism813, and a projection lens 814.

The polarization-illuminating device 50 may consist of a light-sourceunit 60 and a polarized-light generating device 70. The light-sourceunit 60 emits non-polarized light including an S-polarized lightcomponent and a P-polarized light component. The light emitted from thelight-source unit 60 is converted by the polarized-light generatingdevice 70 into specific linearly polarized light (S-polarized light inthis embodiment) having a substantially aligned polarizing direction, toilluminate an illumination region. The three light valves 803, 805, and811 are equivalent to the illumination region.

The polarized-light generating device 70 may consist of a first opticalcomponent 200 and a second optical component 600. The first opticalcomponent 200 is a lens array arranged in a matrix of small lenseshaving a rectangular profile. The second optical component 600 mayconsist of an optical element 300 and an emitting-side lens 390.

The optical element 300 may consist of a condensing lens array 310 andtwo polarizing conversion elements 320 a and 320 b. The condensing lensarray 310 is of the same structure as that of the first opticalcomponent 200, and is arranged in the direction opposing the firstoptical component 200. The condensing lens array 310 has a function,together with the first optical component 200, for respectivelycondensing plural partial light beams divided by each small lens 201 ofthe first optical component 200 to guide them toward incident regions ofpolarizing conversion elements 320 a and 320 b. The polarizingconversion elements 320 a and 320 b are formed by arranging thepolarizing conversion elements 320 (FIG. 8) produced by themanufacturing method according to the present invention so thatrespective polarization separating films 331 and respective reflectingfilms 332 symmetrically oppose each other about the optical axis, bysandwiching it. Therefore, the light beam emitted from the light-sourceunit 60 is converted into substantially specific linearly polarizedlight (S-polarized light in this embodiment) by the polarized-lightgenerating device 70.

The emitting-side lens 390 has a function for superimposing each ofplural sub light beams emitted from the optical element 300 onrespective liquid-crystal light-valves 803, 805, and 811.

The light emitted from the polarization-illuminating device 50 isseparated into colored light beams of three colors, red, green, and blueby the dichroic mirrors 801 and 804 as a color separating opticalsystem. Each of separated colored light beams of the three colors ismodulated corresponding to given image information (image signals) byrespective liquid-crystal light-valves 803, 805, and 811 for each color.These liquid-crystal light-valves 803, 805, and 811 correspond to thelight-modulating device according to the present invention. Each ofmodulated colored light beams by the liquid-crystal light-valves 803,805, and 811 is combined by the cross-dichroic prism 813 as a colorsynthesizing optical system to be projected onto a screen 815 by theprojection lens 814 as a projection optical system. Thereby, colorimages are displayed on the screen 815. In addition, the structure andthe function of each unit of the projector shown in FIG. 7 are disclosedin detail by the applicant of this application in Japanese UnexaminedPatent Application Publication No. 10-177151, for example, so that thedescription thereof is not given in this application.

Since the polarizing conversion elements 320 a and 320 b produced by themanufacturing method according to the present invention are used in thepolarization-illuminating device 50 of the projector 800, themanufacturing cost of the apparatus can be reduced.

While the projector 800 shown in FIG. 7 has been described withreference to an example in which the polarizing conversion elementproduced by the manufacturing method according to the present inventionis used in the polarization-illuminating device in a projector fordisplaying color images, it is apparent that the element is not solimited, but can be applied to various devices. For example, it may beapplied to a projector for projecting monochromatic images. In thiscase, in the apparatus shown in FIG. 7, one liquid-crystal light-valveis only needed, and the color separation optical system for separatingthe light into colored beams of three colors and the color synthesizingoptical system for combining colored beams of three colors can beeliminated. Furthermore, the present invention can be applied to aprojector using only one light valve. Also, the present invention can beapplied to an image display apparatus using illuminating polarized-lightsuch as a projector using a reflection-type liquid-crystal light-valveand a rear-type display apparatus.

In addition, the present invention is not limited to the above-describedexamples and embodiments, and it is intended to embrace all suchvariations and modifications that fall within the spirit and scope ofthe invention.

What is claimed is:
 1. A method for manufacturing a polarizing beamsplitter array that comprises a polarizing conversion element thatconverts non-polarized light into specified polarized light, said methodcomprising: preparing k sets of light transmissive members, k being aninteger of 2 or greater, each of the sets comprising a plurality offirst light transmissive plates and a plurality of second lighttransmissive plates; preparing (k+1) third light transmissive plateshaving a greater thickness than those of the first light transmissiveplates and the second light transmissive plates; producing a compositeplate member by alternately arranging and bonding one set of theplurality of first light transmissive plates and the plurality of secondlight transmissive plates to each of spaces between the (k+1) thirdlight transmissive plates, and alternately arranging a plurality ofpolarization separating films and a plurality of reflecting films ineach interface between the first light transmissive plates, the secondlight transmissive plates and the third light transmissive plates in thecomposite plate member; producing a block substrate having a lightreceiving surface and a light emitting surface by cutting the compositeplate member along a first section parallel to a surface inclining at apredetermined angle “θ” with a surface of the composite plate member,the light receiving surface and the light emitting surface being inparallel to the first section; polishing the light receiving surface andthe light emitting surface of the block substrate; and producing kpolarizing beam splitter arrays from one of the block substrates bydividing the block substrate along a plane that is perpendicular to thefirst section at positions of the third light transmissive plates thatare disposed inside the block substrate.
 2. The method according toclaim 1, preparing the k sets of light transmissive members comprising:forming the polarization separating film on a first surface of the firstlight transmissive plate; and forming the reflecting film on a secondsurface of the first light transmissive plate.
 3. The method accordingto claim 1, preparing the k sets of light transmissive memberscomprising: forming the polarization separating film on one surface ofthe first light transmissive plate; and forming the reflecting film onone surface of the second light transmissive plate.
 4. A method ormanufacturing a polarizing beam splitter array that comprises apolarizing conversion element that converts non-polarized light intospecified polarized light, said method comprising: preparing k sets oflight transmissive members, k being an integer of 2 or greater, each ofthe sets comprising a plurality of first light transmissive plates and aplurality of second light transmissive plates; preparing (k+1) thirdlight transmissive plates having a greater thickness than those of thefirst light transmissive plates and the second light transmissiveplates; producing a composite plate member by alternately arranging andbonding one set of the plurality of first light transmissive plates andthe plurality of second light transmissive plates to each of spacesbetween the (k+1) third light transmissive plates, and alternatelyarranging a plurality of polarization separating films and a pluralityof reflecting films in each interface between the first lighttransmissive plates, the second light transmissive plates and the thirdlight transmissive plates in the composite plate member; producing ablock substrate having a light receiving surface and a light emittingsurface by cutting the composite plate member along a first sectionparallel to a surface inclining at a predetermined angle “θ” with asurface of the composite plate member, the light receiving surface andthe light emitting surface being in parallel to the first section; andproducing k polarizing beam splitter arrays from one of the blocksubstrates by dividing the block substrate along a plane that isperpendicular to the first section at positions of the third lighttransmissive plates that are disposed inside the block substrate.
 5. Themethod according to claim 4, preparing the k sets of light transmissivemembers comprising: forming the polarization separating film on a firstsurface of the first light transmissive plate; and forming thereflecting film on a second surface of the first light transmissiveplate.
 6. The method according to claim 4, preparing the k sets of lighttransmissive members comprising: forming the polarization separatingfilm on one surface of the first light transmissive plate; and formingthe reflecting film on one surface of the second light transmissiveplate.
 7. A method for manufacturing a polarizing conversion elementthat converts non-polarized light into specified polarized light, saidmethod comprising: preparing k sets of light transmissive members, kbeing an integer of 2 or greater, each of the sets comprising aplurality of first light transmissive plates and a plurality of secondlight transmissive plates; preparing (k+1) third light transmissiveplates having a greater thickness than those of the first lighttransmissive plates and the second light transmissive plates; producinga composite plate member by alternately arranging and bonding one set ofthe plurality of first light transmissive plates and the plurality ofsecond light transmissive plates to each of spaces between the (k+1)third light transmissive plates, and alternately arranging a pluralityof polarization separating films and a plurality of reflecting films ineach interface between the first light transmissive plates, the secondlight transmissive plates and the third light transmissive plates in thecomposite plate member; producing a block substrate having a lightreceiving surface and a light emitting surface by cutting the compositeplate member along a first section parallel to a surface inclining at apredetermined angle “θ” with a surface of the composite plate member,the light receiving surface and the light emitting surface being inparallel to the first section; polishing the light receiving surface andthe light emitting surface of the block substrate; producing kpolarizing beam splitter arrays from one of the block substrates bydividing the block substrate along a plane that is perpendicular to thefirst section at positions of the third light transmissive plates thatare disposed inside the block substrate; and producing the polarizingconversion element by selectively bonding λ/2 phase films on the lightemitting surface of the polarizing beam splitter array.
 8. The methodaccording to claim 7, preparing the k sets of light transmissive memberscomprising: forming the polarization separating film on a first surfaceof the first light transmissive plate; and forming the reflecting filmon a second surface of the first light transmissive plate.
 9. The methodaccording to claim 7, preparing the k sets of light transmissive memberscomprising: forming the polarization separating film on one surface ofthe first light transmissive plate; and forming the reflecting film onone surface of the second light transmissive plate.
 10. A method formanufacturing a polarizing conversion element that convertsnon-polarized light into specified polarized light, said methodcomprising: preparing k sets of light transmissive members, k being aninteger of 2 or greater, each of the sets comprising a plurality offirst light transmissive plates and a plurality of second lighttransmissive plates; preparing (k+1) third light transmissive plateshaving a greater thickness than those of the first light transmissiveplates and the second light transmissive plates; producing a compositeplate member by alternately arranging and bonding one set of theplurality of first light transmissive plates and the plurality of secondlight transmissive plates to each of spaces between the (k+1) thirdlight transmissive plates, and alternately arranging a plurality ofpolarization separating films and a plurality of reflecting films ineach interface between the first light transmissive plates, the secondlight transmissive plates and the third light transmissive plates in thecomposite plate member; producing a block substrate having a lightreceiving surface and a light emitting surface by cutting the compositeplate member along a first section parallel to a surface inclining at apredetermined angle “θ” with a surface of the composite plate member,the light receiving surface and the light emitting surface being inparallel to the first section; producing k polarizing beam splitterarrays from one of the block substrates by dividing the block substratealong a plane that is perpendicular to the first section at positions ofthe third light transmissive plates that are disposed inside the blocksubstrate; and producing the polarizing conversion element byselectively bonding λ/2 phase films on the light emitting surface of thepolarization beam splitter array.
 11. The method according to claim 10,preparing the k sets of light transmissive members comprising: formingthe polarization separating film on a first surface of the first lighttransmissive plate; and forming the reflecting film on a second surfaceof the first light transmissive plate.
 12. The method according to claim10, preparing the k sets of light transmissive members comprising:forming the polarization separating film on one surface of the firstlight transmissive plate; and forming the reflecting film on one surfaceof the second light transmissive plate.
 13. A method for manufacturing apolarizing beam splitter array that comprises a polarizing conversionelement that converts non-polarized light into specified polarizedlight, said method comprising: preparing a set of light transmissivemembers, comprising a plurality of first light transmissive plates and aplurality of second light transmissive plates; preparing two third lighttransmissive plates having a greater thickness than those of the firstlight transmissive plates and the second light transmissive plates;producing a composite plate member by alternately arranging and bondingone set of the plurality of first light transmissive plates and theplurality of second light transmissive plates between the two thirdlight transmissive plates, and alternately arranging a plurality ofpolarization separating films and a plurality of reflecting films ineach interface between the first light transmissive plates, the secondlight transmissive plates and the third light transmissive plates in thecomposite plate member; producing a block substrate having a lightreceiving surface and a light emitting surface by cutting the compositeplate member along a first section parallel to a surface inclining at apredetermined angle with a surface of the composite plate member, thelight receiving surface and the light emitting surface being in parallelto the first section; polishing the light receiving surface and thelight emitting surface of the block substrate; and dividing a polarizingbeam splitter array into a plurality of polarizing beam splitter arraysby cutting the polarizing beam splitter array along a second section inparallel with a surface substantially perpendicular to a longitudinaldirection of the plurality of polarization separating films and theplurality of reflecting films arranged inside the polarizing beamsplitter array.
 14. The method according to claim 13, preparing the setof light transmissive members comprising: forming the polarizationseparating film on a first surface of the first light transmissiveplate; and forming the reflecting film on a second surface of the firstlight transmissive plate.
 15. The method according to claim 13,preparing the set of light transmissive members comprising: forming thepolarization separating film on one surface of the first lighttransmissive plate; and forming the reflecting film on one surface ofthe second light transmissive plate.
 16. A method for manufacturing apolarizing beam splitter array that comprises a polarizing conversionelement that converts non-polarized light into specified polarizedlight, said method comprising: preparing a set of light transmissivemembers, comprising a plurality of first light transmissive plates and aplurality of second light transmissive plates; preparing two third lighttransmissive plates having a greater thickness than those of the firstlight transmissive plates and the second light transmissive plates;producing a composite plate member by alternately arranging and bondingone set of the plurality of first light transmissive plates and theplurality of second light transmissive plates to each of spaces betweenthe two third light transmissive plates, and alternately arranging aplurality of polarization separating films and a plurality of reflectingfilms in each interface between the first light transmissive plates, thesecond light transmissive plates and the third light transmissive platesin the composite plate member; producing a block substrate having alight receiving surface and a light emitting surface by cutting thecomposite plate member along a first section parallel to a surfaceinclining at a predetermined angle with a surface of the composite platemember, the light receiving surface and the light emitting surface beingin parallel to the first section; producing a polarizing beam splitterarray from one of the block substrates by dividing the block substrateat positions of the third light transmissive plates that are disposedinside the block substrate; and dividing the polarizing beam splitterarray into a plurality of polarizing beam splitter arrays by cutting thelight transmissive block along a second section in parallel with asurface substantially perpendicular to a longitudinal direction of theplurality of polarization separating films and the plurality ofreflecting films arranged inside the light transmissive block.
 17. Themethod according to claim 16, preparing the set of light transmissivemembers comprising: forming a polarization separating film on a firstsurface of the first light transmissive plate; and forming a reflectingfilm on a second surface of the first light transmissive plate.
 18. Themethod according to claim 16, preparing the set of light transmissivemembers comprising: forming a polarization separating film on onesurface of the first light transmissive plate; and forming a reflectingfilm on one surface of the second light transmissive plate.
 19. A methodfor manufacturing a polarizing conversion element that convertsnon-polarized light into specified polarized light, said methodcomprising: preparing a set of light transmissive members, comprising aplurality of first light transmissive plates and a plurality of secondlight transmissive plates; preparing two third light transmissive plateshaving a greater thickness than those of the first light transmissiveplates and the second light transmissive plates; producing a compositeplate member by alternately arranging and bonding one set of theplurality of first light transmissive plates and the plurality of secondlight transmissive plates between the two third light transmissiveplates, and alternately arranging a plurality of polarization separatingfilms and a plurality of reflecting films in each interface between thefirst light transmissive plates, the second light transmissive platesand the third light transmissive plates in the composite plate member;producing a block substrate having a light receiving surface and a lightemitting surface by cutting the composite plate member along a firstsection parallel to a surface inclining at a predetermined angle with asurface of the composite plate member, the light receiving surface andthe light emitting surface being in parallel to the first section;polishing the light receiving surface and the light emitting surface ofthe block substrate; dividing a polarizing beam splitter array into aplurality of polarizing beam splitter arrays by cutting the polarizingbeam splitter array along a second section in parallel with a surfacesubstantially perpendicular to a longitudinal direction of the pluralityof polarization separating films and the plurality of reflecting filmsarranged inside the polarizing beam splitter array; and producing thepolarizing conversion element by selectively bonding λ/2 phase films onthe light emitting surface of the polarizing beam splitter array. 20.The method according to claim 19, preparing the set of lighttransmissive members comprising: forming a polarization separating filmon a first surface of the first light transmissive plate; and forming areflecting film on a second surface of the first light transmissiveplate.
 21. The method according to claim 19, preparing the set of lighttransmissive members comprising: forming a polarization separating filmon one surface of the first light transmissive plate; and forming areflecting film on one surface of the second light transmissive plate.22. A method for manufacturing a polarizing conversion element thatconverts non-polarized light into specified polarized light, said methodcomprising: preparing a set of light transmissive members, comprising aplurality of first light transmissive plates and a plurality of secondlight transmissive plates; preparing two third light transmissive plateshaving a greater thickness than those of the first light transmissiveplates and the second light transmissive plates; producing a compositeplate member by alternately arranging and bonding one set of theplurality of first light transmissive plates and the plurality of secondlight transmissive plates to each of spaces between the two third lighttransmissive plates, and alternately arranging a plurality ofpolarization separating films and a plurality of reflecting films ineach interface between the first light transmissive plates, the secondlight transmissive plates and the third light transmissive plates in thecomposite plate member; producing a block substrate having a lightreceiving surface and a light emitting surface by cutting the compositeplate member along a first section parallel to a surface inclining at apredetermined angle with a surface of the composite plate member, thelight receiving surface and the light emitting surface being in parallelto the first section; producing a polarizing beam splitter array fromone of the block substrates by dividing the block substrate at positionsof the third light transmissive plates that are disposed inside theblock substrate; and dividing the polarizing beam splitter array into aplurality of polarizing beam splitter arrays by cutting the lighttransmissive block along a second section in parallel with a surfacesubstantially perpendicular to a longitudinal direction of the pluralityof polarization separating films and the plurality of reflecting filmsarranged inside the light transmissive block; and producing thepolarizing conversion element by selectively bonding λ/2 phase films onthe light emitting surface of the polarizing beam splitter array. 23.The method according to claim 22, preparing the set of lighttransmissive members comprising: forming a polarization separating filmon a first surface of the first light transmissive plate; and forming areflecting film on a second surface of the first light transmissiveplate.
 24. The method according to claim 22, preparing the set of lighttransmissive members comprising: forming a polarization separating filmon one surface of the first light transmissive plate; and forming areflecting film on one surface of the second light transmissive plate.